Field of the Invention
The invention lies in the semiconductor technology field. More specifically, the present invention relates to a semiconductor configuration having an optical fuse (fuse link), which is composed of a material that can absorb radiation energy in at least one specific wavelength band, and having a packing material at least partially adjoined by the optical fuse.
Recently, optically programmable fuses have been used, inter alia, preferably in semiconductor memory configurations. There they are used, for example, to activate redundant elements during a wafer test. Such a wafer test is used, for example, to determine faulty memory cells and to replace them by redundant memory cells, by blowing fuses and/or antifuses.
Once semiconductor configurations have left the xe2x80x9cwafer levelxe2x80x9d and, in order to remain with the example of semiconductor memory configurations, are packed in packs as memory modules, it is currently impossible to repair faulty or weak memory cells at the module level, or to replace them by redundant memory cells, by blowing fuses.
For this reason, modules which indicate faults in a final test at the module level (backend test), such as drift after burn-in (load test), are rejected. In other words, at the moment, it is impossible to use optical fuses to repair semiconductor configurations at the module level.
It is accordingly an object of the invention to provide a semiconductor configuration with an optical fuse, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which allows repairs at the module level by blowing the fuse.
With the foregoing and other objects in view there is provided, in accordance with the invention, a semiconductor configuration, comprising:
an optical fuse composed of a material selected from the group consisting of an AIIIBV semiconductor material, titanium silicide, germanium, PbS, InSb, and SiGe and configured to absorb radiation energy in a given wavelength band; and
a packing material adjoining the optical fuse and being permeable to the radiation energy in the given wavelength band.
In accordance with an added feature of the invention, the optical fuse is partially adjacent the packing material.
In other words, the radiation energy can at least partially pass through the packing material in the specific wavelength band. In this context, the term packing material means, in an entirely general form and for example, also the semiconductor body or the substrate, or a carrier for the semiconductor configuration.
The fuse in the semiconductor configuration according to the invention absorbs radiation energy in a different wavelength band to that of the packing material of the semiconductor configuration.
In accordance with an additional feature of the invention, the packing material is silicon and the AIIIBV semiconductor material is InGaAsP.
For example, in the case of Rambus CSP (Rambus=DRAM architecture, such as SDRAM; CSP=Chip Size Package), the rear face of the pack (or package) consists of the bare silicon of the chip which contains the semiconductor configuration. A material is then chosen for the fuses which are arranged on the front face of the chip, which absorbs radiation energy in a band to which the pack material is transparent, that is to say silicon in the present example. So-called III-V material, or AIIIBV semiconductor materials are suitable, for example, for use as this material. InGaAsP is particularly advantageous as the fuse material if the packing material is formed by the chip of the semiconductor configuration. Other materials are also suitable for the fuses, such as metals, standard alloys, other alloys, germanium, PbS, InSb, SiGe etc. Examples include standard metallizations for integrated circuits based on tungsten or aluminum, copper and titanium silicide.
Silicon has a radiation energy absorption coefficient which decreases sharply at wavelengths above about 950 nm and is virtually transparent in the wavelength band above 1050 nm. If a laser with a wavelength of about 1350 nm is used for the radiation energy, then the laser radiation passes through the silicon of the chip virtually without any impediment. Radiation in the 1350 nm wavelength band is, however, absorbed to an excellent extent by all the AIIIBV semiconductor materials, so that fuses composed of these AIIIBV semiconductor materials can be blown by the inference of laser radiation.
The invention thus makes it possible to repair semiconductor configurations at module level in a final test, after they have been packed, by blowing fuses, if faults are found in a final test. This is achieved by using materials through which radiation energy can pass for the packing of the module, that is to say for the semiconductor configuration pack, while the fuses which are used for the repair are composed of materials which absorb all the radiation energy which is passed through the packing.
The invention can advantageously be applied to semiconductor memory configurations. However, the invention can, of course, also be used expediently with other semiconductor configurations in which redundant components are switched on by blowing a fuse, in order to replace faulty components as required.
In the semiconductor configuration according to the invention, the fuse must be provided such that it is at least partially accessible through the packing material for the radiation energy which acts from the exterior on the semiconductor configuration. This can be achieved by providing the fuse on the top face of a semiconductor chip whose silicon body itself forms the packing.
However, the present invention can, of course, also be applied to other forms of the packing; the only critical feature is that radiation energy which is absorbed by the fuse can pass through the packing, and that the radiation energy can act on the fuse via the packing.
It should also be mentioned that the term xe2x80x9cpackingxe2x80x9d means a housing in the general sense which protects the semiconductor configuration, that is to say the integrated circuit contained in it. In the above example, the packing is formed by the chip itself.
The packing can also be soldered on a module as, for example, in the case of an RIMM (Rambus Inline Memory Module). The only critical feature is that the fuses remain accessible through the packing for radiation energy, and that they can absorb this radiation energy.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in semiconductor configuration with an optical fuse, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.